Unna's Orcein-Aniline Blue
for Elastic


A red nuclear stain
Solution A
Acetic acid, glacial 1 mL
Distilled water 1 L
Solution B
Aniline blue 0.5 g
Orcein 0.5 g
Acetic acid, glacial   2.5 mL
Ethanol, 100% 25 mL
Distilled water 50 mL
Glycerol 10 mL
Dissolve the aniline blue in the water with heat. Cool and filter. Dissolve the orcein in the ethanol. Add the acetic acid and glycerol. Combine the solutions.

Tissue sample
5µ paraffin sections of neutral buffered formalin fixed tissue are suitable. Other fixatives are likely to be satisfactory.


  1. Bring sections to water via xylene and ethanol.
  2. Stain the nuclei with a red nuclear stain.
  3. Place into solution A for a few minutes.
  4. Place into solution B for 1-10 hours.
  5. Differentiate with solution A until elastic fibres are clear.
  6. Dehydrate with 95% and absolute ethanols.
  7. Clear with xylene and mount with a resinous medium.

Expected results


  1. Gatenby & Beams specified water blue rather than aniline blue
  2. Unna's method has been more commonly applied in conjunction with other methods, such as Pasini's trichrome, with solution B (Unna's solution) being incorporated into other staining solutions.


Gray, Peter. (1954)
The Microtomist's Formulary and Guide.
Originally published by:– The Blakiston Co.
Republished by:– Robert E. Krieger Publishing Co.
    Gatenby, J. B. & Cowdry, E. V., (1928)
    Bolles Lee's Microtomist's Vade Mecum, pp. 280
    Blakiston, Philadelphia




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